Alarm control method

Abstract

A drive current for driving actuators is generated based on a first digital signal comprising n-bit binary data which is supplied from a microprocessor and it is applied to an excitation coil. The drive current is supplied to the exciting coil and is converted into a voltage which is then converted into a second digital signal comprising n-bit binary data. The binary data of the second digital signal is compared with the digital data of the first digital signal to detect an alarm condition. Furthermore, the second digital signal is compared with first and second reference value to set plural alarm conditions.

What is claimed is: 
     
       1. An alarm control method comprising the steps of: providing a first digital signal having n bits, n being a positive integer, from a processor circuit having an analog/digital function, and controlling a current flowing through at least one actuator in accordance with the first digital signal;   generating a second digital signal having n bits, based on a value of a current actually flowing through said at least one actuator;   comparing digital data of said first digital signal with digital data of said second digital signal; and   detecting an alarm condition when said digital data of the second digital signal is greater than that of the first digital signal.   
     
     
       2. The method of claim 1 further comprising the steps of: terminating said step of providing of said first digital signal when said alarm condition is detected; and   responding to said alarm condition, including determining a relationship between said second digital signal and a reference value greater than said first digital signal.   
     
     
       3. The alarm control method of claim 2 wherein said determining step uses first and second non-identical reference values. 
     
     
       4. The alarm control method of claim 3 including producing an alarm signal in response to the alarm condition and: wherein said actuator is powered in normal operation;   wherein said second reference value is greater than said first reference value;   wherein when the second digital signal is less than both the first and second reference values, said alarm signal is produced;   wherein when the second digital signal is greater than the first reference value but less than the second reference value, the alarm signal is produced and power is cut off to said actuator; and   wherein when the second digital signal is greater than the first and second reference values, the alarm signal is produced and power is immediately cut off to said actuator.   
     
     
       5. The alarm control method of claim 1 wherein said processing circuit includes a microprocessor. 
     
     
       6. The method of claim 5 wherein said first and second digital signals are compared in said microprocessor. 
     
     
       7. An alarm control method comprising the steps of: providing a first digital signal having n bits, n being a positive integer, from a processor circuit having an analog/digital function;   controlling a current flowing through at least one actuator in accordance with the first digital signal, including converting said first digital signal to a first analog signal;   providing a feedback signal to said processor circuit indicative of a current actually flowing in said actuator;   generating in said processor circuit a second digital signal having n bits, based on said actuator current;   comparing in said processor circuit digital data of said first digital signal with digital data of said second digital signal;   comparing said second digital signal with a reference value; and   selectively providing an alarm signal based on said comparing step.   
     
     
       8. The method of claim 7 further comprising selectively terminating a power supply that is used in said step of controlling a current, said terminating being based on said comparing step.